hi guyz...I guess this is a stupid question..erm...my friend recently suggest me to install one pod filter to increase the performance..but I have no idea about wat a pod filter is and would be very appreciated if anyone can explain to me....also...can u guys tell me which brand is good for BMWs?? coz my friend wanna do me one for free...but I dunnno which brand to choose...Thanks soooo much!!! haf fun!!!